Muscle characteristics and fatigue properties after spinal cord injury

Spinal cord injury (SCI) results in a myriad of changes in paralyzed skeletal muscle. Many of these changes stem from the disruption in nerve activation and lead to a loss of muscle mass and the transformation of muscle fiber types to a predominance of type II fast-twitch fibers. Changes to muscle contractile properties are also commonly reported, however, the results are not yet conclusive and appear to vary with the muscle examined. The presence or absence of spasticity also appears to be a significant variable, acting to preserve some muscle characteristics following paralysis. The purpose of this review is to summarize the current literature examining changes in skeletal muscle after SCI, with a particular focus on the effect on fatigue resistance. Mechanisms of fatigue in able-bodied muscle are discussed in the context of their potential to explain the decreased fatigue resistance observed after SCI.